The design of high-power radio frequency (RF) devices capable of operating at high frequencies and bandwidths has generally involved minimizing impedances in order to produce high power levels at high frequencies while at the same time controlling the heat output associated with high-power operation in order to avoid functional failure. Small reactive impedances are usually associated with smaller dimensions. Smaller dimensions, however, may lead to the heat problem associated with high-power applications.
A method involving band-splitting, processing signals with multiple narrowband circuits, and then summing or multiplexing the results has been used for achieving broader bandwidths. This technique, however, may require tuning individual circuits to match specific impedances to avoid signal loss due to unbalanced loads and line reflections. If impedances are mismatched, individual RF power transistors in the individual circuits are sometimes surrounded by passive components, such as resistors, capacitors, and inductors, and each RF power transistor may be tuned at its inputs and outputs with the addition of external, or off-chip, passive components. Even though some passive components can be formed on-chip, inductors generally must remain off-chip, leading to large transistor devices with complex and area-consumptive external passive impedance matching networks.